The invention concerns a switchable support element for a valve train of an internal combustion engine, said support element having an outer housing, an inner element, a hydraulic clearance compensation element and a coupling means, the outer housing being installed with an outer peripheral surface in a reception of a cylinder head and comprising a longitudinal bore within which, in an uncoupled state, the inner element is axially displaceable, the inner element comprising a further bore in which a pressure piston having a head and forming a part of the clearance compensation element is received, said coupling means comprising at least one bore extending in radial or in secant direction in each of the inner element and the outer housing and at least one associated slide, said bores being aligned to each other in a relative position of the inner element and the outer housing, and the slide being partially displaceable by an actuating means from the bore of the outer housing into the bore of the inner element for achieving coupling.
A switchable support element of the -pre-cited type is known from DE 44 22 340 A1. For a return movement of its inner element in cam direction, this support element comprises a so-called lost motion compression spring which increases the design length. The bore for the slide in the inner element extends radially through the entire inner element and is arranged beneath the clearance compensation element in axial direction. This is an unfavorable stacked-up construction. Since, for example, cooling water ducts and gas exchange channels extend in the immediate vicinity of the reception for the support element in the cylinder head, the installation depth available for the relatively long support element is limited, or complicated modifications must be made to existing cylinder heads. However, such modifications are often not possible because they would interfere with flow conditions, particularly in the gas exchange channels.
The object of the invention is therefore to provide a switchable support element of the pre-cited type in which the mentioned drawbacks are eliminated by simple measures.
The invention achieves this object by the fact that the bore of the inner element is made as a pocket bore whose axial line intersects the further bore of the inner element.
In this way, the aforesaid drawbacks are eliminated by simple measures. The prior art stacked arrangement of the clearance compensation element and the bore for the slide in the inner element is avoided. Thus, a switchable support element is obtained that has a shorter design length than the above-mentioned prior art solutions and can thus be installed more easily in existing cylinder head constructions.
It goes without saying that it is also possible to use a plurality of circumferentially spaced coupling means which results in better load-bearing properties.
In an advantageous embodiment of the invention, the actuating means for the slide that is made, for instance, as a rod, is installed in a housing that extends in the cylinder head and adjoins the reception of the outer housing. It is proposed at the same time to create a simple anti-rotation device for the inner element relative to the outer housing through the inner end of a section of the housing. In addition, an upper stop for the inner element relative to the outer housing can also be realized in this region. Due to these measures, further anti-rotation and upper stop means can be dispensed with. Advantageously, the housing for the actuating means is arranged in a region of the cylinder head that intersects neither the above-mentioned cooling ducts and gas exchange channels nor spark plug holes, camshaft bearings and the like.
Thus, for the most part, the slide with its actuating means is situated outside of the support element and is applied to this only in radial or in secant direction. However, it is also conceivable to make the slide engage at a slant or to effect a direct coupling, for instance, through balls, catches or pins actuated by the slide so that the slide itself is not a directly engaging element.
According to another advantageous feature of the invention, the slide is actuated electromagnetically or hydraulically. For example, the outer end surface of the slide can define a pressure chamber for hydraulic medium, or the slide can be configured as an actuator rod comprising an armature plate for electromagnetic actuation.
According to a final proposition of the invention, a means for re-setting the slide against the force of the electromagnetic or hydraulic actuating means may also be installed in the housing. This a further -measure towards reducing the dimensions of the switchable support element.
The scope of the invention also includes a solution in which the support element is not completely but only partly disconnectable from cam lift. It is also conceivable to realize switching steps by arranging bores for the slide at different heights in the inner element.